In a large skillet, deep sauté pan, or Dutch oven, brown the ground beef over medium-high heat. Cook until no pink remains, breaking it up with a wooden spoon.
Add the diced onion and minced garlic to the skillet. Cook for about 4-5 minutes until the onion is soft and translucent. Drain any excess grease from the pan.
Stir in the taco seasoning packet, beef broth, salsa, and uncooked pasta. Stir well to combine and ensure the pasta is mostly submerged.
Bring the mixture to a boil. Once boiling, cover the pan with a tight-fitting lid, reduce the heat to low, and simmer for 12-15 minutes, or until the pasta is tender.
Remove the pan from the heat. Stir in the sour cream (if using) and the shredded cheddar cheese until completely melted and a creamy sauce forms.
Garnish with fresh cilantro, sliced jalapeños, or black olives if desired. Serve immediately while hot and gooey.